In the spirit of "the Red Headed League", I have copied
the following statement from the Encyclopaedia Britannica; "The character
of Holmes…partly derives from a teacher at Edinburgh noted for his deductive
reasoning" [The New Encyclopaedia Britannica, Doyle, Sir Arthur Conan,
(15th ed. 1978)]

Specifically, as stated in Conan Doyle, Portrait of
an Artist, by Julian Symons (The Mysterious Press 1979) at pages 19,20;

"Conan Doyle always said the model for
these deductive skills was Dr. Joseph Bell, surgeon at Edinburgh
Infirmary, and one of the professors at Edinburgh University when Conan
Doyle was a medical student, In appearance Bell was thin
and dark, with piercing gray eyes and a narrow aquiline nose, so
that he had some resemblance to the imaged Sherlock Holmes. [Doyle] used
the Bell deductive approach when he began to write the stories. Dr. Bell
modestly said that Conan Doyle had exaggerated his powers"

Consistent with the above is Conan Doyle, A Biographical
Solution, by Ronald Pearsall (St. Martin’s Press 1977) at pages 10,56,
where it is stated " Joseph Bell, surgeon at the Edinburgh Infirmary, was
transmuted into Sherlock Holmes. Bell considered that Doyle’s medical education
had taught him to be observant" Moreover, the following may be found in
an article entitled The Man Who Hated Sherlock Holmes, The Life of Arthur
Conan Doyle: "[Doyle] then went on tostudy medicine at Edinburgh University, where he came
under the influence of Dr. Joseph Bell, the model for Holmes, a surgeon
who astonished his students with uncanny displays of observation and deduction.
"See, The Weekly Standard – August 30 / September 6, 1999, at page 31.

Finally, the following account of Dr. Bell is set forth
in an essay entitled " The Original of Sherlock Holmes" by Dr. Harold Emery
Jones:

"All Edinburgh medical students remember Joseph Bell
– Joe Bell – as they called him. Always alert, always up and doing, nothing
ever escaped that keen eye of his. He read both patients and students like
so many open books. His diagnosis was almost never at fault. "This, gentlemen" announced [Professor
Bell], "contains a very potent drug. To the taste it is intensely
bitter. It is most offensive to the sense of smell. But I want you to test
it by smell and taste; and, as I don’t ask anything of my students
which I wouldn’t be willing to do myself, I will taste it before passing
it round"

Here he dipped his finger in the liquid, and placed
it in his mouth. The tumbler was passed round. With wry and sour faces
the students followed the Professor’s lead. One after another tasted the
liquid; varied and amusing were the grimaces made. The tumbler, having
gone the round, was returned to the Professor. "Gentlemen", said he, with
a laugh, " I am deeply grieved to find that not one of you has developed
this power of perception, which I so often speak about; for if you watched
me closely, you would have found that, while I placed my forefinger in
the medicine, it was the middle finger which found its way into my mouth"

These methods of Bell impressed Doyle greatly at the
time. The impression was a lasting one. This essay was found in an
old volume of selected works of Arthur Conan Doyle. See Conan Doyle’s Best
Books – In Three Volumes Illustrated, B.F. Collier & Son, Publishers
– Sherlock Holmes Ed. (__?__).

In summary, although Dr. Bell may not have been the
only model for Sherlock Holmes, he seems to have been the primary one.
Thanks to Dr. Bell, at least in part, Sir Arthur Conan Doyle made deduction
and the power of perception central to the Sherlock Holmes stories.